1. Field of the Invention
This invention relates to a heat transfer recording apparatus and a facsimile apparatus for transferring the ink of an ink sheet to a recording medium to thereby effect recording of images on the recording medium.
Here, the term "heat transfer recording apparatus" covers, in addition to a facsimile apparatus, apparatuses having a recording function such as an electronic typewriter, a copying apparatus and a printer apparatus.
2. Related Background Art
Generally, a thermal transfer printer uses an ink sheet having heat-meltable (or heat-sublimatable) ink applied to a base film, and selectively heats the ink sheet in correspondance with an image signal by a thermal head, and transfers the melted (or sublimated) ink to recording paper to thereby accomplish image recording. Generally, this ink sheet is such that the ink is completely transferred to the recording paper after a signal image recording operation (a so-called one-time sheet) and therefore, it has been necessary that after the termination of the recording of one character or one line, the ink sheet be conveyed by an amount corresponding to the length of the recording and then the unused portion of the ink sheet be reliably brought to the recording position. This has led to the tendency that the amount of ink sheets used increases and the running cost of the heat transfer printer becomes high as compared with an ordinary thermosensitive printer in which recording is effected on thermosensitive paper.
In order to solve such a problem, as disclosed in Japanese Laid-Open Patent Application No. 57-83471, Japanese Laid-Open Patent Application No. 58-201686 and Japanese Patent Publication (examined) No. 62-58917, there have been proposed thermal transfer printers in which the recording paper and ink sheet are conveyed with a velocity difference provided therebetween. As described in the aforementioned publications, there is known an ink sheet capable of plural (n) times of image recording (a so-called multiprint sheet), and if such an ink sheet is used, when a record length L is to be continuously recorded, recording can be accomplished with the conveyed length of the ink sheet conveyed after or during each image recording being made less than the length L (L/n:n&gt;1). Thereby, the efficiency of use of the ink sheet is increased to n times, and a reduction in the running cost of the heat transfer printer can be expected. This recording system will hereinafter be referred to as multiprint.
In the case of the multiprint using such an ink sheet, the ink of the ink layer of the ink sheet is heated divisionally n times, and during each such heating, a shearing force is produced between the ink of the ink layer which is melted or sublimated and the ink which is not melted or sublimated to thereby accomplish the transfer of the ink to recording paper. During this transfer recording, a velocity difference is provided between the conveyance velocity of the recording paper and the conveyance velocity of the ink sheet and therefore, a great load is exerted on a recording paper conveying motor when, for example, after the recording of one line, the recording paper is conveyed for the recording of the next line. This may lead to the undesirable possibility that under the great influence of the quantity of black information (the number of heat generating dots) in the recording data of one line, the conveyance of the recording paper becomes irregular corresponding to the recording data and the recording interval becomes non-uniform. Therefore, it is conceivable to employ a recording paper conveying motor of greater torque, but this leads to the problem of increased cost of the apparatus. Also, if the torque of the motor is increased, overshoot, residual vibration or the like may be produced during the recording of a line imposing a small load and thereby cause noise or adversely affect the conveyance of the recording paper.